Nailbiting or hair pulling
Everyone has some nervous habit. Most of the time, our little quirky ways of fidgeting don't cause any serious problems -- other than occasional embarrassment. I have friends who make fun of the way I frequently say "okay!" when I finish something and am trying to motivate myself for the next task.
But I have met business men who hide their hands behind their backs when they are offered a hand to shake. They are too self-conscious of their obviously chewed-off fingernails. And I have met teenage girls who wore hats all the time -- to keep the bald spot on their scalps from showing and unsuccessfully keeping the hair from being available to twirl and pull out.
Nailbiting (onychophagia) and hair pulling (trichotillomania) and similar habits (such as skin picking) are usually responses to stress or boredom. The habit can start very early in life -- when we were infants or toddlers -- so hypnotherapy is especially effective at getting to the root which lies back before conscious memory in most cases. Since most nail biters and hair pullers notice the after effects of these habits and not the process, many feel as if they act in a trance, and that is probably the case. So in 3 to 6 sessions, we would bring that unconscious urge to bite or pull back up to a conscious level where the habit can be controlled. Little by little, you learn to catch yourself earlier and earlier until you notice the urge and dismiss it immediately without damaging your body.